Regarding an image having a luminance component and a color-difference component, the image is sometimes encoded after converting a resolution of the color-difference component. In the same manner, the image is decoded after converting the resolution of the color-difference. The resolution of the color-difference component has various formats such as a 4:4:4 format, a 4:2:2 format, and a 4:2:0 format.
If resolution conversion is performed repeatedly with respect to the color-difference component, it leads to deterioration of the image. For that reason, in the past, there have been attempts to suppress the image deterioration. More particularly, a technology has been disclosed in which a filter that meets the conditions for suppressing the image deterioration is designed as the filter to be used in performing resolution conversion with respect to the color-difference component.
However, in the past, image deterioration occurs depending on the resolution of the color-difference component of the image to be output.